It always looks more professional when drapery rods have fully covered fabric returns (be it panels and/or valances.

(However, if the drapery wall is viewed ONLY from a head-on position then it may matter somewhat less about the returns being covered. Do not forget though that the light from outside will sneek through that 4- or 5-inch fabricless space between the wall and the drapery panel/valance.)

So, would you advise against the decorative pole treatment that seems so popular (obviously those never have returns due to their design) and go with a traditional double traverse rod?

The "return" doesn't have to be of metal. It can be of "nothing". Just put an eye hook in the wall at the same level as the holes/rings on the front of the deco rod that your pleats will be hanging from.

Place a drapery hook through the fabric at the side hem edge of the panel and hook it into the wall eyehook. Drapery hook all of the pleats on the rings (or whatever holes) on the rod. In other words, the fabric beyond the last pleat IS the return. Hope that makes sense.

You CAN get decorative traverse rods. Not sure if this will help you get the look you want.

Here is a link that might be useful: wood pole traverse rod